(1) Field of the Invention
The present invention relates to an apparatus and method for distinguishing a cough from a sneeze, and in particular to an apparatus and method of comparing the sound and volume attributes of possible cough events by a test subject within a plethysmograph against evaluation criteria to ascertain which events are probably coughs.
(2) Description of the Prior Art
The affects of various gases and aerosols on test subjects, e.g., rats and mice, are determined in laboratory research by enclosing a test subject, e.g., a mouse or rat, in the test chamber of a laboratory testing device known as a plethysmograph. A gas or aerosol is introduced into the chamber and the respiratory patterns of the test subject are evaluated by measuring changes in the pressure within the test chamber.
Plethysmographs are comprised of a test chamber to enclose the test subject, a reference chamber, and a differential pressure transducer connected to the two chambers, e.g., via tubing extending from a port in each chamber to the transducer. Both chambers are in communication with the ambient air, i.e., the air within the room where the tests are being conducted, through inlet ports or pneumotachographs.
As changes to the air volume within the test chamber occur, pressure variations are recorded by the transducer, which normally displays the recorded data in numerical form or as a graph. Air pressure within the test chamber can also vary due to changes in the pressure of air entering the test chamber through the pneumotachographs. The transducer simultaneously measures variations in air pressures within the two chambers, and subtracts the reference chamber measurements from the animal chamber measurements. As a result, the net pressure variations are essentially attributable to the respiration patterns of the test animal. Preferably, the test and reference chamber pneumotachographs are close to each other to minimize variations in exterior air patterns.
A representative plethysmograph of the type used to measure small animal pulmonary responses is shown and described in commonly assigned U.S. Pat. No. 5,379,777 to Lomask, the entire disclosure of the patent being incorporated herein by reference.
One of the criteria measured is the number of time that the test animal coughs during a given time. The number of coughs can be measured to observation, with the tester listening for the coughs. However, this system is tedious, time consuming and inaccurate. Further, there is a degree of uncertainty due to the fact that a cough is often difficult to distinguish from a sneeze due to the similarity of their sound and their limited duration. Therefore, there is a need for an apparatus and method for automating the process of counting coughs during such experiments, and in particular for distinguishing between coughs and sneezes that occur.